Pallet carriers of the above-specified type are known in various forms and are employed in program-controlled milling and drilling machines as well as machining centers so as to permit rapid and safe changing of the works loaded on pallets. One of the basic prerequisites for the repeated performance of identical machining operations to be carried out on the changed works is the automatic and high-precision positioning of the switched pallets on the pallet carrier and their firm mounting in the respective prescribed machining positions. With known pallet carriers there arises the problem that the pallets at the end of their transfer movement rest directly on the slideways and upon insertion of the centering bolts still have to perform some slight lateral adjusting movements in the transitional regions between static friction and sliding friction before the hydraulic clamping members become fully effective. This affects the precise positioning of the pallet on the pallet carrier.
Further, it has been found that the operability of full automatic machine tools is significantly reduced by deposits constituted of solid particles, fine chips and the like on the slide faces of the various slideways. When some object such as a pallet moves across these slide faces, said deposits will be urged into the frequently employed ductile slideway linings and will result in damage to the fine-finished slide faces.